Mutations can inhibit this tumour-suppressive effect, and somatic mutations of the p53 gene have been found in a wide range of tumours, often with concomitant loss of the normal allele.6.7 Initial reports for human bladder cancer,8 and our own work, revealed a wide variety of point mutations in urothelial cancer. Mutations in p53 have been reported in most muscle-invasive bladder carcinomas,4,8 but infrequently in non-invasive urothelial cancers. In this patient we found identical somatic cell alterations of the c-erbB-2 and p53 genes in renal cell and bladder tumours. The high level of c-erbB-2 gene amplification is rare in bladder cancer, and it is most unlikely that the identical point mutation at codon 282 of the p53 gene would have arisen by chance from separate mutations, especially since codon 282 is not a known "hot spot" for p53 mutations.7 It seems probable therefore that the bladder cancer arose as a result of distal tumour cell spread from the primary renal pelvis tumour, rather than there being two tumours arising locally as independent clones in some sort of "field change". This conclusion is also consistent with knowledge that urinary tract transitional cells are readily shed and that tumour cells can be recovered from urine or bladder washings. Cancer Research Unit, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK
J. LUNEC C. CHALLEN
Pathology Department, Royal Victoria Infirmary, Newcastle upon Tyne,
University Department of Surgery and Department of Urology, Freeman Hospital, Newcastle upon Tyne
K. MELLON D. E. NEAL
patients.’ We obtained fresh bedding from the pet shop that supplied the snake and original bedding material. Although this bedding resembled chipped bark whereas the original sample resembled wood shavings, the shop owner claimed that the two beddings came from the same source and were of the same quality. This claim was substantiated when we again isolated many sahnonellae. These isolates were not serotyped, but on the basis of API 20E tests, no S arizonae seemed to be present, indicating that the strains of this organism found originally were derived from the snake and not from the bedding itself. Similar bedding from a second shop contained no salmonella. In addition to the probable contribution of the snake’s commensal flora to the salmonella content of the original sample, as well as that of the bark bedding, dietary factors might have played a part. Since the snake was fed largely on raw mince, food chain/food poisoning strains could also have been introduced into the salmonella cocktail. We feel that this case shows the potential health hazards associated with keeping a reptilian pet. The reptile’s natural intestinal flora, its diet, its bedding, and its contained warm environment could combine to produce a thriving population of pathogenic bacteria. Department of Applied Biochemistry
1. Fujita J, Srivasta SK, Kraus MH, Rhim JS, Tronick SR, Aaronson SA. Frequency of molecular alterations affecting ras proto-oncogenes in human urinary tract tumours. Proc Natl Acad Sci USA 1985; 82: 3849-53. 2. Wright C, Mellon K, Neal DE, Johnston P, Corbett IP, Home CHW. Expression of c-erbB-2 protein product in bladder cancer. Br J Cancer 1990; 62: 764-65. 3. Neal DE, Sharples L, Smith K, Fennelly JA, Hall RR, Harris AL. The epidermal growth factor receptor and the prognosis of bladder cancer. Cancer 1990; 65: 1619-25. 4. Wright C, Mellon K, Johnston P, et al. Expression of mutant p53, c-erbB-2 and the epidermal growth factor in transitional cell carcinoma of the human urinary bladder. Br J Cancer 1991; 63: 967-70. 5. Yamamoto T, Ikawa S, Akiyama T, et al. Similarity of protein encoded by the human c-erbB-2 gene to epidermal growth factor receptor. Nature 1986; 319: 230-34. 6. Harris AL. Cancer genes: telling changes of base. Nature 1991; 350: 377-78. 7. Levine AJ, Momand J, Finlay CA. The p53 tumour suppressor gene. Nature 1991; 351: 453-55. 8. Sidransky D, von Eschenbach A, Tsai YC, et al. Identification of p53 gene mutations in bladder cancer and urine samples. Science 1991; 252: 706-08.
carried salmonella and 61-9% of tested strains were S arizonae.1 S arizonae, although not a major food-poisoning strain, has been implicated in human illness, especially in immunocompromised
pet snake and its
bedding SIR,-over the past 15 months we have been investigating the food sources in sporadic cases of salmonellosis in Nottinghamshire. Our investigations are based mainly on interview with the patient at the earliest possible opportunity to obtain a careful dietary history, which is supplemented by sampling and testing of suspect foods when possible. A 1-year-old boy had Salmonella typhimurium infection with no dietary history of suspect foods. On further inquiry we discovered that the family kept a pet garter snake which the child handled frequently, under supervision. We sampled a 1 g piece of woodchip bedding from the snake tank, which was made of glass and heated with a lamp. After enrichment culture, well over a hundred presumptive salmonella colonies were obtained, of which 28 were analysed. Although complete serotyping was not attempted, on the basis of ribotyping analysis we believe that at least 5-7 salmonella types were present-including S arizonae (61 % of all isolates), S typhimurium (4%), and S takoradi (25%), which is a rare strain previously reported in sludge samples in Verona and Glasgow, and in Italian foxes. Reptiles carry salmonella, and there is a strong link between reptiles and S arizonae in particular, since reptiles were the source of the first S arizonae strains characterised.1 In an Israeli survey, 26 of 33 (79%) snakes tested carried salmonella, and 77% of these were S arizonae.2 In a report from Finland, 21 of 25 (84%) reptiles tested
and Food Science,
Faculty of Agricultural and Food Sciences, University of Nottingham, Loughborough, Leics LE12 5RD, UK
R. A. S. PLUMMER S. J. BLISSETT C. E. R. DODD
Greenberg Z, Giladi I, Bouskila A, et al. Salmonella from reptiles in the Arava region, Israel. IsrJ Med Sci 1987; 23: 859. 2. Le Minor L. Genus III Salmonella Lignieres 1900, 389AL, In: Krieg N, Hold J, eds. Bergey’s manual for systemic bacteriology, vol 1. Baltimore: Williams and Wilkins, 1.
Junttila J, Pajula T, Schildt R. Salmonella in Finnish pets. Suomen Elainlaakarilehti 1988; 94: 87-93. 4. Kraus A, Guerra-Batista G, Alarcon-Segovia D. Salmonella arizona arthritis and septicemia associated with rattlesnake ingestion by patients with connective tissue disease. A dangerous complication of folk medicine. J Rheumatol 1991; 18: 3.
Litigation over congenital scalp defects SIR,-Recently I have been approached twice by parents who believed that their child’s scalp had been injured during surgical induction of labour or by a fetal scalp electrode, and I know of two other cases. Because some years had passed before medicolegal advice had been sought (and one child had had plastic surgery) I asked the parents to identify, from a display of some twenty slides of scalp defects and injuries, the lesion most resembling that of their child’s at birth. They both identified typical aplasia cutis congenita, a condition with an incidence of around 1 in 6000 births, which most frequently affects the scalp in the region of the hair swirl. Typically, there is a round, punched-out area about 1 cm across lacking skin and subcutaneous tissues. The surrounding hair may be absent too or altered in colour. The defect heals by scarring, which is often present at birth. The pathogenesis is unknown but it is sometimes familial or associated with trisomy 13-15. Birth attendants should be aware of this congenital anomaly; neonatal records should be correctly annotated; and parents should be given a full explanation at the time. Department of Child Health, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
PETER M. DUNN
CORRECTION Cassava cyanogens and konzo, an upper motoneuron disease found in Africa. -In this article by Dr Tylleskär and colleagues (Jan 25, p 208), the units for serum thiocyanate in fig 2 should be Nmol/1.